Improvement in pistons for steam-engines



UNITED 'STATES PAT-ENT OFFICE.

NATHAN P. STEVENS, OF BOSTON, MASSACHUSETTS.

IMPROVEMENT IN PISTONS FOR STEAM-ENGINES.

Specification forming part of Letters Patent No. 48,851, dated July 18, 1865.

To all whom it 'may concern:

Be it known that LNATHAN P. STEvENs,ot` Boston, in the county ot Suffolk and State ot' Massachusetts, have made a new and useful invention having reference to engine-cylinders and expansion-pistons used therein; and I do hereby declare the same to be fully described in the following specication and represented in the accompanying drawings, ot' which- Figure 1 is a longitudinal section, and Fig. 2 a transverse section, of an engine cylinder and piston provided with my invention. Fig. 3 is a side view of the piston. Fig. 4 is an edge view ot' the ring separate from the piston.

The expansive piston to which my invention is applicable is represented at A and the engine-cylinder at B in the said figures, the head of the piston having a groove, ce, in and around its circumference, such groove being vfor the reception of a split ring or annulus, b,

which has a width very` little less than that of the groove,both ring and groove being rectangular in their transverse sections. In order to prevent the ring from turning around in the groove I employ a pin or projection, c, to extend from the piston-head into the ring or between its ends'. Vhere the said pin or projection goes between the ends of the ring each zontal or inclined to the horizomthe same being so that the weight ot' the `piston and the pressure of the steam tending to force the piston downward may co-operate with the lower surfaces of the piston and bore of the cylinder in breaking the joint or open spaces at the ends of the ring and keeping the steam from blowing through such joint or space.

. In the drawings,the engine-piston is shown as having the joint of the expansive ring arranged at the bottom of the piston-head and on the bore of the cylinder. The ring is also exhibited as provided under such connection with the pin or projection c', extending from the piston-head and between the ends of the ring, in order to prevent the said ring from so turning around in the piston-head as to materially varythe positions of the ends of the ring' with respect tothe bottom of the piston-head and the bottom of the bore ofthe cylinder.

l/Vith au expansive ring so made and applied to a piston and its cylinder the steam, when pressing against either end of the piston-head in order to move the piston,will pass underneath the packing or expansion ring and expand it againstthe boreof the cylinder, so as to prevent the passage of steam by the said packing-ring. Vere the joint of the ring at the top otthe piston-head the steam would blow through the joint,t`or the reason. that the diameter of the piston-head has to be somewhat less than that ot the bore of the cylinder, and therefore there will be space between the upper part ofthe piston-head and the contiguous surface of the bore. As the piston-head atits bottoni will b'e in eontactwith the bore, no such space will be formed immediately at the place of contact, and here it is that I arrange the opening of the ring, and thus by such arrangement of it I cause it to be so covered that no steam canpass through it.

What, therefore, I claim as my invention 1s- Arranging thej'ointot1 the expansion-ringat the lower part of the piston-head and on the bottom of the -bore of the cylinder, and providing 'such ring and piston with a means of preventing the ring from revolving in its groove, the whole being substantially as and for the purpose set forth.

N. P. STEVENS.

Witnesses: l

R. H. EDDY, F. P. HALE, Jr. 

